1. Field of the Invention
The present invention relates to a wet type electrophotographic image forming apparatus. More particularly, the present invention relates to a wet type electrophotographic image forming apparatus having an oxidation catalyst device for removing developer vapor from the fuser through oxidation, and a method for controlling the oxidation catalyst device.
2. Description of the Related Art
A general example of wet type electrophotographic image forming apparatus scans a laser beam onto a photosensitive medium to form an electrostatic latent image thereon. A developing solution attaches to the photosensitive medium to visualize the latent image. The visualized image is transported onto a suitable recording medium. The wet type electrophotographic image forming apparatus provides an advantage over a dry-type electrophotographic image forming device utilizing powder-type developer, particularly in terms of providing clearer printouts. The wet type electrophotographic image forming apparatus is also suitable for producing high quality color images.
FIG. 1 schematically shows the structure of a conventional wet type electrophotograhic image forming apparatus 100, which comprises an image forming apparatus body 110, photosensitive drums 121, 122, 123, 124, charging devices 131, 132, 133, 134, light exposure devices 141, 142, 143, 144, developing devices 151, 152, 153, 154, a transfer belt 160, first transfer rollers 171, 172, 173, 174, a second transfer roller 180 and a fuser 190.
The developing devices 151, 152, 153, 154 each have different colors of developer therein, and supplies respective color developers to the photosensitive drums 121, 122, 123, 124. Developer is usually a mixture of ink to develop the image, and a carrier usually in liquid state such as Norpar. Norpar is a hydrocarbon solution, which is the mixture of C10H22, C11H24, C12H26, C13H28. As the developer is attached to the photosensitive drums 121, 122, 123, 124, a latent image is visualized. The visualized image is then transported by the first transfer rollers 171, 172, 173, 174 to the transfer belt 160, and transported by the second transfer roller 180 onto a suitable recording medium. The recording medium is transported to the fuser 190. The ink of the developer has settled onto the recording medium when the recording medium passes through the fuser 190. The liquid carrier is evaporated by the high heat into an inflammable hydrocarbon gas such as methane CH4 and is exhausted.
The hydrocarbon gas, which is classified into volatile organic compound (VOC) group, usually pollutes ambient air, and generates a bad small when discharged without suitable treatment. In order to avoid such problems, various methods have been suggested to remove the hydrocarbon gas.
Among a variety of suggested methods, currently available methods mainly comprise filtering, which physically removes the gaseous component by use of carbon filter such as activated carbon, direct combustion, which bums the gaseous component at temperature ranging from 600° C. to 800° C., and or oxidation, which decomposes the gaseous component into water and carbon dioxide at a relatively low temperature ranging from 150° C. to 400° C. by use of suitable catalyst.
Filtering using the carbon filter is incapable of decomposing the carrier, and therefore needs be replaced at regular intervals when the amount of collected carrier exceeds a predetermined extent. The direct combustion method has safety issues due to use of high temperature heat.
With the above considered, oxidation catalyzing is deemed to be the most effective method and most popularly used due to its high decomposition efficiency and safety.